Live-Attenuated RSV Vaccine Shows Immunogenicity in Children: Journal of Infectious Diseases

Respiratory syncytial virus (RSV) is a significant cause of lower respiratory illness (LRI) in pediatric populations. With the need for an effective vaccine, Ruth Karron and team have explored RSV/6120/ΔNS2/1030s, a cDNA-derived live-vaccine candidate. The findings were published in The Journal of Infectious Diseases.

To evaluate the safety and immunogenicity of the RSV/6120/ΔNS2/1030s vaccine, a double-blind, placebo-controlled trial was conducted. The trial administered a single intranasal dose of the vaccine at different levels of plaque-forming units (PFU) to two groups: 15 RSV-seropositive children aged 12 to 59 months and 30 RSV-seronegative children aged 6 to 24 months. The vaccine-to-placebo ratio was 2:1.

The study found that RSV/6120/ΔNS2/1030s was able to infect 100% of the RSV-seronegative children and demonstrated immunogenicity, as evidenced by the geometric mean RSV plaque-reduction neutralizing antibody titer (RSV-PRNT) of 1:91. Furthermore, the vaccine proved to be genetically stable. However, researchers observed mild rhinorrhea (runny nose) occurring more frequently in vaccinated children (18 out of 20) compared to those who received the placebo (4 out of 10) during the trial period. Notably, only one vaccinee experienced LRI during a period when only the vaccine virus was detected.

Following the RSV season, 5 out of 16 vaccinees exhibited significant rises (≥4-fold) in RSV-PRNT, with substantially higher titers compared to the 4 out of 10 placebo recipients with rises. This indicated that RSV/6120/ΔNS2/1030s primed for strong anamnestic (memory) neutralizing antibody responses following naturally-acquired RSV infection.

The RSV/6120/ΔNS2/1030s vaccine candidate has shown promise as an immunogenic and genetically stable option for RSV-seronegative children aged 6 to 24 months. It was able to induce primary neutralizing serum antibody responses and potent memory antibody responses in this population. However, the study also revealed a higher frequency of rhinorrhea in vaccinated children compared to those who received the placebo.

While the vaccine's safety profile warrants further investigation, the positive results in terms of immunogenicity and anamnestic responses provide hope for a potential solution to combat RSV in vulnerable pediatric populations.

Reference:

Karron, R. A., Luongo, C., Woods, S., Oliva, J., Collins, P. L., Buchholz, U. J., Council-Dibitetto, C., Gatto, M., Ghasri, T., Gormley, A., Herbert, K., Jordan, M., Loehr, K., Morsell, J., Soro, P., … Wanionek, K. (2023). Evaluation of the live-attenuated intranasal respiratory syncytial virus (RSV) vaccine RSV/6120/ΔNS2/1030s in RSV-seronegative young children. In The Journal of Infectious Diseases. Oxford University Press (OUP). https://doi.org/10.1093/infdis/jiad281